Feature Request: Support custom slash commands from .github/prompts directory

[AungMyoKyaw]

Feature Request: Custom Slash Commands Support

Description

The GitHub Copilot CLI should support custom slash commands (similar to Claude Code's custom commands) by reading prompt files from a .github/prompts/ directory, just like the GitHub Copilot VS Code extension does.

Current Behavior

Currently, when using copilot and typing a slash command, only built-in commands are available. Custom prompt files stored in .github/prompts/*.prompt.md are not recognized or available as slash commands.

Expected Behavior

When users have prompt files in their repository like:

• .github/prompts/openspec-apply.prompt.md
• .github/prompts/openspec-archive.prompt.md
• .github/prompts/openspec-proposal.prompt.md

These should automatically appear as available slash commands when using the Copilot CLI, allowing users to select and use these custom prompts in their current session.

Proposed File Structure

.github/prompts/
├── openspec-apply.prompt.md
├── openspec-archive.prompt.md
└── openspec-proposal.prompt.md

Example Expected UX

1. User runs copilot
2. User types /
3. The following options appear:
   • /openspec-apply (from .github/prompts/openspec-apply.prompt.md)
   • /openspec-archive (from .github/prompts/openspec-archive.prompt.md)
   • /openspec-proposal (from .github/prompts/openspec-proposal.prompt.md)
   • [built-in commands...]

Benefits

• Consistency with GitHub Copilot VS Code extension behavior
• Enables repository-specific custom commands and workflows
• Improves developer productivity with reusable prompts
• Supports team-wide standardization of common operations

References

• This functionality already exists in GitHub Copilot VS Code extension
• Similar feature exists in Claude Code as "custom commands"